1. Technical Field
The present invention relates to a control device for an automatic transmission having at least an automatic shift mode and a temporary manual mode.
2. Related Art
There are automatic transmissions which have, in addition to an automatic shift mode where shifting is automatically performed in accordance with the state in which the vehicle is traveling, a temporary manual mode (temporary manual gearshift mode) where, when the driver performs a gearshift operation (e.g., operating a downshift paddle switch or operating an upshift paddle switch) while in automatic shift mode, the transmission is shifted down or shifted up in accordance with the gearshift operation. In order to cancel this temporary manual mode, the driver needs to perform operations satisfying cancelation conditions. Cancelation conditions include, for example, operation of a shift lever, maintaining steady-state traveling for a predetermined amount of time, or a kick-down operation (e.g., full-open of the accelerator pedal).
Now, there are cases where engine revolutions have dropped due reduced speed or the like, in a state where the driver has shifted to select a high-speed transmission gear (e.g., a case where the driver has selected a high-speed transmission gear to suppress fuel consumption) in temporary manual mode. In this case, even if the driver requests acceleration by operating the accelerator, there are cases where engine torque necessary for acceleration cannot be generated due to the low engine revolutions. In this case, acceleration in response to the driver's intent to accelerate cannot be realized due to insufficient drive force. Obtaining sufficient acceleration in such a case requires shifting down from the current transmission gear.
Shifting down from the current transmission gear requires an operation of canceling the temporary manual mode to return to the automatic shift mode (e.g., operating a shift lever or performing accelerator operations to maintain steady-state traveling for a predetermined amount of time) or performing a gearshift operation (e.g., operating a paddle switch for downshifting). This operation must be made in addition to acceleration operations of requesting acceleration, which may seem troublesome to the driver. Although the temporary manual mode may be cancelled by a kick-down operation, kick-down control generates a great change in drive force, so the acceleration may be rapid, unlike the acceleration that the driver intended.
There are automatic transmission control devices where the vehicle automatically performs downshifting during temporary manual mode, even if the driver has not performed gearshift operations. For example, Japanese Unexamined Patent Application Publication (JP-A) No. 2012-122549 discloses automatically downshifting transmission gears in a case where a predetermined traveling state is identified during temporary manual mode.
The technology disclosed in JP-A No. 2012-122549 controls deceleration by downshifting in a case where sudden deceleration is identified in temporary manual mode, due to the driver suddenly letting up on the accelerator or braking. However, the technology disclosed in JP-A No. 2012-122549 does not automatically downshift in a case where the driver has performed acceleration operations while in the temporary manual mode. Accordingly, acceleration in response to the driver's intent to accelerate cannot be realized when the state of the vehicle is such that acceleration is insufficient in the transmission gear that the driver has selected.